Optimize OP_ADD in edits loading

During loading the edits journal FSEditLog.loadEditRecords() processes OP_ADD inefficiently. It first removes the existing INodeFile from the directory tree, then adds it back as a regular INodeFile, and then replaces it with INodeFileUnderConstruction if files is not closed. This slows down edits loading. OP_ADD should be done in one shot and retain previously existing data.